A short circuit while the cruise control accelerates causes the problem.

Khodrocar - The National Highway Traffic Safety Administration is advising the owners of 4.8 million million vehicles in the United States from Fiat Chrysler Automobiles not to use the cruise control because the system might not disengage even if the driver presses the brake or manually attempts to turn it off. If the problem occurs, owners need to shift the gearbox into neutral, apply the brakes, and put the vehicle in park after coming to a stop.

In a statement, FCA said that an "unlikely sequence of events" would be necessary for this failure to happen. The cruise control would need to be accelerating the vehicle – like for a road grade – at the same time that a short circuit in the system occurs. The driver then wouldn't be able to deactivate the cruise. The brakes would still work, but owners would find an easier time slowing down by shifting into neutral because the cruise would be trying to accelerate.

"FCA US is unaware of any related injuries or accidents involving the affected vehicles, which span six model-years and account for more than 200 billion travel miles," the automaker reported in its statement.

FCA will send letters to affected owners as soon as next week, and dealers will install upgraded software for the powertrain control module.

The automaker will also recall 490,000 vehicles for this issue in Canada, according to Transport Canada. There will also be an undisclosed numbers in Mexico and in certain markets outside of the NAFTA region.